城市建筑垃圾填埋区地下水水质对比和溯源

Comparison and source apportionment of groundwater quality in urban construction waste landfill areas

从我国两个典型中小型城市各选取一处建筑垃圾填埋场,采用熵权指数法(EWQI)对两场地周边地区地下水水质进行综合评价分析,基于聚类分析等手段进行初步污染源识别,并在此基础上采用正定矩阵分解(PMF)模型进行源解析计算,定量解析和对比两处建筑垃圾填埋场地对周边区域地下水水质变化的贡献.结果表明,建筑垃圾的填埋处理可能会引起周边地下水水质恶化,其影响程度与场地性质、填埋历史、介质防污性能等因素有关.两处研究场地中,场地1周边地下水水质恶化情况更严重,有7种检测组分的浓度超过了地下水质量标准(GB/T 1448-2017)中的III类标准限值,而场地2有1种组分超标.对地下水化学组分进行源解析的结果表明,两处场地均识别出岩土矿物溶解、溶质运移、农业、建筑垃圾和工业活动这5种自然和人为来源,场地1周边区域各来源贡献占比分别为18.2%、18.0%、25.9%、19.5%、9.8%,场地2占比分别为19.8%、23.5%、18.9%、12.6%和15.1%.人类活动和建筑垃圾填埋污染对场地1周边地下水的影响大于对场地2的影响.

In this study,two landfill sites mainly disposing construction and demolition wastes(CDW)were selected from two typical small or medium-sized cities in China.An entropy weighted water quality index was used to evaluate the groundwater quality in surrounding areas of the two sites.An integrated source apportionment approach was developed to reduce the uncertainty of the inverse modelling process.The sources of chemical composition in groundwater was firstly identified using multivariate statistical methods such as cluster analysis.Then a positive matrix factorization(PMF)model was used for source apportionment calculation,quantifying the contributions of two CDW landfills to changes in groundwater compositions in surrounding areas.Results showed that CDW landfill site could make groundwater quality deteriorate,with the degree of the impact depending on a variety of factors such as site properties,landfill history,and contamination prevention capacity of vadose zone.The overall deterioration of groundwater quality in the surrounding area of site 1was more severe than that of site 2.The concentration of seven monitored compositions in site 1exceeded the class III standard limit of the groundwater quality standard(GB/T 14848-2017),while only one composition in site 2exceeded the limit.The PMF source analysis identified five natural and anthropogenic sources for the chemical compositions of groundwater in both locations,namely dissolution of minerals in soils and rocks,solute transport,agricultural sources,CDW sources and industrial sources.The contributions of these sources were 18.2%,18.0%,25.9%,19.5%and 9.8%in site 1,and 19.8%,23.5%,18.9%,12.6%and 15.1%in site 2,respectively.The impact of human activities and CDW landfill on the groundwater surrounding site 1is greater than that on site 2.